Purpose: To assess the separate and interactive effects of illness severity, job factors, psychosocial variables and other predictors on disability among persons with asthma. In addition to activities limitations, disability is defined to mean: work cessation or change in hours of work, job, employer or job duties. Significance: Disability among those with asthma is common and costly. Little is known about the causes of disability in asthma; experience with other chronic diseases suggests that illness severity alone does not adequately predict disability. There is a theoretical and experimental basis upon which to postulate that other variables, including factors such as job flexibility, asthma self-efficacy, social supports, and cigarette smoking may be predictors of disability in asthma. The proposed study will help explicate the inter-relationships among illness severity, other co-factors and disability in asthma, addressing a major research gap. Design: Random sample of 40 board certified pulmonologists in Northern California enrolling persons with asthma for this study. Pulmonologists will maintain a log of all persons meeting a clinical definition of asthma presenting to their offices for treatment over a one month period. I will enroll 600 subjects with any history of laborforce participation, to be interviewed by a trained survey worker in order to assess severity of disease using a severity scale based on symptoms, medications, and past-asthma history. Interviews will use established survey instruments to assess psychosocial variables, smoking exposure and work history. Approximately 400 subjects working at the time of baseline interview will be re-studied for 2 follow-up interviews over the course of the study. Analysis: Cross-Sectional Study. With data from the baseline survey I will use logistic regression to estimate the separate and combined impact of illness severity and other variables on work disability. Longitudinal Study. I will use a Cox proportional hazards model to estimate the time until work disability as a function of the same risk factors of interest. Anticipated Results: Based on preliminary data and previous experiences with a similar sampling frame in a longitudinal study, the proposed study will provide statistically powerful estimates of the separate and combined impact of risk factors for disability among persons with asthma.